1. Field of the Invention
The invention relates to an implantable medical device such as an implantable cardiac pacemaker or an implantable cardioverter defibrillator (ICD). However, the invention is not limited to these specific implantable medical devices but instead fundamentally includes all electronically controlled implantable medical devices.
2. Description of the Related Art
Such implantable medical devices, e.g., cardiac pacemakers or ICDs, are often equipped with a bidirectional wireless interface today, making it possible to program these medical devices by means of an external device or to make data inquiries of the medical devices, e.g., physiological data acquired by the medical device. Based on the fact that implantable medical devices should have the smallest possible volume and therefore necessarily have only a limited amount of energy, which is usually available through a battery, for their operation, it is customary for the respective bidirectional wireless interface not to remain permanently in operation but instead to be activated preferably only when actually needed. The total energy consumption of the bidirectional wireless interface can be kept within limits over a longer period of time in this way. The bidirectional wireless interface can thus change back and forth between an OFF state and an ON state, such that the bidirectional wireless interface consumes little or no energy in the OFF state and is capable of wireless reception and transmission of data only in the ON state.
For this reason, such medical devices require an activation mechanism for programming over a bidirectional wireless interface to activate the bidirectional wireless interface of the medical device. For activation of the bidirectional wireless interface, i.e., to cause the bidirectional wireless interface to switch from an OFF state to an ON state, it is customary today to provide activators in the form of separate external devices or a programming head for inductive telemetry of a conventional programming device. It can also be anticipated that additional low-current receivers will be provided in a frequency range other than that of the bidirectional wireless interface for activation of the bidirectional wireless interface in the future.
Disadvantages of the aforementioned approaches include the fact that it is an additional external device, which is associated with costs, problems in introducing the external device into the sterile area in an operating room or the risk of loss of the external device or the disadvantages of an additional receiver in the implantable medical device. The latter causes costs, consumes power and must be approved. Furthermore, antenna tuning is critical when using a second high frequency because a compromise must be made here between the frequencies of the additional receiver for activation of the bidirectional wireless interface and the frequencies for the bidirectional wireless interface or a second antenna must be integrated into the electronic implant.